Endocrine

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Author:
sgustafson
ID:
61139
Filename:
Endocrine
Updated:
2011-01-21 18:10:38
Tags:
endocrine
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Description:
Diabetes
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  1. sulfonylurea
    stimulate B-cells to release insulin
  2. biguanides
    • includes metformin
    • inhibit gluconeogenesis, increase GLUT4 translocation
  3. DPP-4 inhibitors
    • decrease degradation of incretins (hormones that stimulate insulin secretion), doesn't cause weight gain
    • SE: pancreatitis
  4. Glucose -> G6P
    • Occurs @ rate dependent on intracellular [glucose]
    • Liver, B-cells: glucokinase (high Km, can serve as glucose sensor-important in B-cells!!; sequestered in nucleus by glucose regulatory protein - glucose stimulates release, F6P stimulates sequestering)
    • Muscle: hexokinase (low Km)
  5. gluconeogenesis
    • lactate, aa's, glycerol
    • pyruvate -pyruvate carboxylase-> OAA -PEPCK-> -Fructose1,6bisphosphatase-> -G6Phosphatase-> glucose
  6. glycogenolysis
    glycogen synthesis
    Glycogen -glycogen phosphorylase-> G1P -> G6P

    Glucose -> G6P -> G1P -glycogen synthase-> glycogen
  7. High levels of glucose
    • glucagon inhibited -> no hepatic glucose release
    • insulin release stimulated -> no hepatic glucose release, uptake of glucose by cells
  8. energy storage sites
    • liver - glycogen, 24hr supply
    • muscle
    • - glycogen - not available for brain
    • -protein - second largest store, not good
    • adipose - fate, largest store
  9. Glucose transporters
    • GLUT2 - liver, B-cells uptake porportional to plasma [glucose], high Km
    • GLUT1
    • GLUT3 - low Km, allows brain to take up same amt of glucose regardless of plasma concentration
  10. GLUT4
    insulin causes glucose transporters to go to the membrane
  11. Points of regulation in glycolysis
    • Phosphofructokinase (PFK-1): F6P->F1,6P
    • Pyruvate kinase (PEP->pyruvate)
  12. Phosphofructokinase regulation
    • Positive: F2,6P, AMP
    • Negative: ATP, citrate, H+
    • Side rxn for regulation only: F6P -PFK-2-> F2,6P
    • PFK-2 is a bifunctional enzyme!!!
  13. Pyruvate kinase regulation
    • Positive: F1,6P
    • Negative: ATP, alanine
    • Glucagon phosphorylates and inactivates
  14. PDK-2 in liver
    • F6P -> F2,6P
    • glucagon increases cAMP, phosphorylation of PFK-2, inhibits glycolysis
    • Insulin dephosphorylates PFK-2, stimulates glycolysis
  15. PDK-2 in heart muscle and skeletal muscle
    • Heart: EPI increases cAMP, PKA activity, but the PFK-2 isoform is activated by phosphorylation. Stimulates glycolysis.
    • Skeletal muscle: bifunctional enz not phosphorylated by PKA. Regulation by intracellular concentration.
  16. Formation of acetyl CoA
    • Pyruvate dehydrogenase (PDH)
    • inhibited by NADH, ATP, acetylCoA
    • Inactivated by phosphorylation
    • Ca2+ activates the phosphatase, which activates the enzyme
  17. PEPCK
    • controls gluconeogenesis
    • controlled by transcription
    • decreased by insulin
    • increased by fasting, glucagon, gluco/thyro-corticoids
  18. fructose-1,6-bisphosphatase regulation
    • opposite of PFK-1
    • positive: citrate
    • negative: AMP, F2,6P
  19. Van Gierke
    • glycogen storage disease
    • G6Phosphatase deficiency
  20. glycogen synthesis/breakdown
    • insulin: dephosphorylation, activates glycogen synthase
    • glucagon: phosphorylation, activates glycogen phosphorylase
  21. Glucagon v. insulin phosphorylation?
    • glucagon acts thru cAMP, PKA to phosphorylate
    • insulin acts thru protein phosphatase, desphosphorylates
  22. Why do patient w/liver failure get hypoglycemia?
    • Depend on the liver to release glucose in fasting state
    • need G6Phosphatase
  23. How does alcohol effect gluconeogenesis?
    • Inhibits it
    • May have low blood sugar the next day
  24. What causes insulin resistance?
    • illness
    • obesity
    • inflammation/cytokines
    • sedentary lifestyle
    • pregnancy
    • cirrhosis
    • genetic factors
    • Remember: 80% will adapt, not become DM2
  25. What is c-peptide?
    • portion cleaved off pro-enzyme to get the active form
    • measured because it has a longer half life than insulin
    • other tests: - anti-GAD, insulin Abs
  26. Liver in diabetes
    • glycogenlysis and gluconeogenesis
    • glycogen synthesis is taking place, but not fast enough
  27. Skeletal muscle in diabetes
    • cannot uptake glucose
    • ion pumps fail
    • K+ loss (whole body)
  28. Fats in diabetes
    • Triglycerides are broken down into free FAs, glycerol -> DKA
    • Normally restrained by insulin
  29. glitazone
    • Thiazolidinediones
    • activation of PPARs
    • - insulin resistance decreased
    • - leptin levels increase
  30. Prevalence of DM1 v DM2
    • 30mil DM2
    • 1.5 mil DM1 in the USA, clusters w/atuoimmune disorders
  31. microvascular complications of diabetes
    • hyperglycemia
    • nephropathy
    • retinopathy
    • neuropathy - amputations, impotence, hypoglycemia
  32. macrovascular complications of diabetes
    • coronary artery disease
    • cerebrovascular disease
    • peripheral vascular disease (amputations)

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